RSUM not giving expected results.

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Hi. I made an OTBI report (check attached image) using the Cash Management - Bank Statements Real Time, Subject Area

I want to do a RSUM of each bank account to get the latest account balance, taking in consideration the flow and making it negative when a debit and keeping the sign when credit. (check code snippet).

And it's not working. It does bring results but have not found a pattern of what it does. Have no idea why. First time using this aggregation function in OTBI. I do use similar functions in SQL but here I'm not sure RSUM is partitioning well.